<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>watch</title>
</head>
<body>
    <div id="app">
        <a href="https://cn.vuejs.org/v2/api/index.html#watch">文档</a>
    </div>
<!-- vue2 -->
<script src="https://cdn.jsdelivr.net/npm/vue@2.6.14"></script>
<script>
    var app=new Vue({
        name: "app",
        el: "#app",
    })
</script>

</body>
</html>